1. Field of Invention
The invention generally relates to optical add-drop multiplexers. More particularly, the invention relates to reconfigurable optical add-drop multiplexers having single channel granularity.
2. Description of Related Art
Most ring-based WDM (wavelength division multiplexed) optical networks deployed today employ a banded architecture where the minimum increment of optical capacity is a band of several wavelengths. This approach makes sense for networks with many wavelengths deployed that may be accessed by fixed optical add-drop multiplexers. The individual wavelengths can be grouped and managed as individual bands to achieve minimal losses when bypassing a node. A significant disadvantage to this banded approach is that wavelengths can be “stranded.” A wavelength is stranded when it cannot be used to establish a link between points A and B because one or more of the other wavelengths in the same band is already in use somewhere between A and B. To minimize the number of stranded wavelengths in the network, wavelength pre-planning is necessary, adding a layer of complexity for communications carriers.
Another issue with the conventional banded architecture is that bands are frequently under-filled. Even if a small number of wavelengths are required for a requested connection between two nodes, a whole band will be dedicated to that connection.